Residual Exertional Dyspnea in Cardiopulmonary Disease

Beyond Spirometry: Linking Wasted Ventilation to Exertional Dyspnea in the Initial Stages of COPD

Exertional dyspnea, a key complaint of patients with chronic obstructive pulmonary disease (COPD), ultimately reflects an increased inspiratory neural drive to breathe. In non-hypoxemic patients with largely preserved lung mechanics - as those in the initial stages of the disease - the heightened inspiratory neural drive is strongly associated with an exaggerated ventilatory response to metabolic demand. Several lines of evidence indicate that the so-called excess ventilation (high ventilation-CO2 output relationship) primarily reflects poor gas exchange efficiency, namely increased physiological dead space. Pulmonary function tests estimating the extension of the wasted ventilation and selected cardiopulmonary exercise testing variables can, therefore, shed unique light on the genesis of patients' out-of-proportion dyspnea. After a succinct overview of the basis of gas exchange efficiency in health and inefficiency in COPD, we discuss how wasted ventilation translates into exertional dyspnea in individual patients. We then outline what is currently known about the structural basis of wasted ventilation in "minor/trivial" COPD vis-à-vis the contribution of emphysema versus a potential impairment in lung perfusion across non-emphysematous lung. After summarizing some unanswered questions on the field, we propose that functional imaging be amalgamated with pulmonary function tests beyond spirometry to improve our understanding of this deeply neglected cause of exertional dyspnea. Advances in the field will depend on our ability to develop robust platforms for deeply phenotyping (structurally and functionally), the dyspneic patients showing unordinary high wasted ventilation despite relatively preserved FEV1.

Sex- and Age-Adjusted Reference Values for Dynamic Inspiratory Constraints During Incremental Cycle Ergometry

Activity-related dyspnea in chronic lung disease is centrally related to dynamic (dyn) inspiratory constraints to tidal volume expansion. Lack of reference values for exertional inspiratory reserve (IR) has limited the yield of cardiopulmonary exercise testing in exposing the underpinnings of this disabling symptom. One hundred fifty apparently healthy subjects (82 males) aged 40 to 85 underwent incremental cycle ergometry. Based on exercise inspiratory capacity (ICdyn), we generated centile-based reference values for the following metrics of IR as a function of absolute ventilation: IRdyn1 ([1-(tidal volume/ICdyn)] x 100) and IRdyn2 ([1-(end-inspiratory lung volume/total lung capacity] x 100). IRdyn1 and IRdyn2 standards were typically lower in females and older subjects (p<0.05 for sex and age versus ventilation interactions). Low IRdyn1 and IRdyn2 significantly predicted the burden of exertional dyspnea in both sexes (p<0.01). Using these sex and age-adjusted limits of reference, the clinician can adequately judge the presence and severity of abnormally low inspiratory reserves in dyspneic subjects undergoing cardiopulmonary exercise testing.

Improving Respiratory Muscle Strength and Overall Function in Patients With Cardiovascular Disease Through Rehabilitation Hospitals

Background

The prevalence of respiratory sarcopenia and its effect on respiratory muscle strength (RMS) in patients with cardiovascular disease (CVD), who are transferred to a convalescent rehabilitation hospital after acute care and require continuous cardiac rehabilitation (CR), is currently unclear. This study aimed to assess changes in RMS, physical function, and activities of daily living (ADL) before and after CR performed in a rehabilitation hospital.

Methods

Of 50 consecutive patients transferred to a rehabilitation hospital for ongoing CR, 30 fulfilled the inclusion criteria. Maximal inspiratory and expiratory pressures (MIP and MEP, respectively) were measured at transfer, and patients with decreased RMS were diagnosed with respiratory sarcopenia. RMS, physical function, exercise tolerance, ADL ability, and health-related quality of life (HR-QoL) were measured and compared at transfer and discharge.

Results

The prevalence of respiratory sarcopenia at the time of transfer to the rehabilitation hospital was 93.3%. RMS assessments at transfer and discharge demonstrated significant improvements in %MIP (from 46.3±26.1% to 63.6±33.7%) and %MEP (from 44.8±17.3% to 56.6±21.8%). Short physical performance battery, gait speed, handgrip strength, and knee extension muscle strength significantly improved, along with significant prolongation of 6-min walking distance as a measure of exercise tolerance. ADL assessment using the functional independence measure revealed significant improvement, as did HR-QoL assessed according to the five-dimension, five-level, EuroQoL instrument, following CR.

Conclusions

Although respiratory sarcopenia was highly prevalent among patients with CVD who required transfer to a rehabilitation hospital after acute care, continuous CR significantly improved RMS, ADL, physical function, and exercise tolerance. These findings support the continued expansion of CR, particularly in dedicated rehabilitation hospitals.

Prognostic significance and clinical determinants of residual dyspnoea at discharge in acute heart failure: a single-centre, prospective observational study

OBJECTIVE

This study aimed to assess the prognostic significance of residual (discharge) dyspnoea in acute heart failure (AHF) patients.

DESIGN

Single-centre, prospective observational study.

SETTING

Patients hospitalised for decompensated AHF in a single cardiology centre, in Poland.

PARTICIPANTS

All patients (n=202) who survived the hospitalisation with the primary diagnosis of AHF and were discharged from the hospital.

PRIMARY AND SECONDARY OUTCOME MEASURES

1-year all-cause mortality; and the composite endpoint of 1-year all-cause mortality and rehospitalisation for the HF (whichever occurred first).

RESULTS

On admission, 159 (78.7%) AHF patients presented dyspnoea at rest, while residual resting dyspnoea at discharge was present in 16 patients (7.9%). There were 48 (24%) patients with moderate/severe exertional dyspnoea at discharge. In the multivariable model, the resting dyspnoea at discharge was related to a higher risk of both 1-year mortality and composite outcome, with HR (95% CI) 8.0 (3.7 to 17.3) and 5.1 (2.6 to 10.2), respectively, both p<0.0001. Analogically, moderate or severe residual dyspnoea at discharge was related to the heightened risk of study both outcomes, with HR (95% CI) 3.1 (1.8 to 5.4) and 1.8 (1.1 to 2.9), respectively, p<0.01.

CONCLUSIONS

Among AHF patients the residual dyspnoea at discharge was unexpectedly common and was associated with an unfavourable outcome during 1-year follow-up.

The pulmonary function laboratory in the investigation of dyspnea of unknown origin

Chronic dyspnea (i.e., dyspnea for at least 3 months) negatively impacts the health-related quality of life of ~10% of the general population. In a sizable fraction of these individuals, the underlying cause remains unclear after detailed clinical assessment, basic pulmonary function tests, and chest imaging, characterizing dyspnea of unknown origin (DUO). The “lung doctor” is frequently called to assess these patients for diagnostic clarification, an endeavor fraught with complexities in most circumstances.

Cardiopulmonary exercise testing applied to respiratory medicine: Myths and facts

Cardiopulmonary exercise testing (CPET) remains poorly understood and, consequently, largely underused in respiratory medicine. In addition to a widespread lack of knowledge of integrative physiology, several tenets of CPET interpretation have relevant controversies and limitations which should be appropriately recognized. With the intent to provide a roadmap for the pulmonologist to realistically calibrate their expectations towards CPET, a collection of deeply entrenched beliefs is critically discussed. They include a) the actual role of CPET in uncovering the cause(s) of dyspnoea of unknown origin, b) peak O₂ uptake as the key metric of cardiorespiratory capacity, c) the value of low lactate ("anaerobic") threshold to differentiate cardiocirculatory from respiratory causes of exercise limitation, d) the challenges of interpreting heart rate-based indexes of cardiovascular performance, e) the meaning of peak breathing reserve in dyspnoeic patients, f) the merits and drawbacks of measuring operating lung volumes during exercise, g) how best interpret the metrics of gas exchange inefficiency such as the ventilation-CO₂ output relationship, h) when (and why) measurements of arterial blood gases are required, and i) the advantages of recording submaximal dyspnoea "quantity" and "quality". Based on a conceptual framework that links exertional dyspnoea to "excessive" and/or "restrained" breathing, I outline the approaches to CPET performance and interpretation that proved clinically more helpful in each of these scenarios. CPET to answer clinically relevant questions in pulmonology is a largely uncharted research field: I, therefore, finalize by highlighting some lines of inquiry to improve its diagnostic and prognostic yield.

Exertional oscillatory ventilation in subjects without heart failure reporting chronic dyspnoea

Oscillatory ventilation detected on incremental cardiopulmonary exercise testing might be found in subjects without heart failure reporting exertional dyspnoea despite the best available therapy for their underlying cardiopulmonary disease https://bit.ly/3Tyl7bE.

Correlation between respiratory muscle weakness and frailty status as risk markers for poor outcomes in patients with cardiovascular disease

AIMS

Although the developmental mechanism of respiratory muscle weakness (RMW) and frailty are partly similar in patients with cardiovascular disease (CVD), their relationship remains unclear. This study aimed to investigate the correlation between RMW and frailty and its impact on clinical outcomes in patients with CVD.

METHODS AND RESULTS

In this retrospective observational study, consecutive 1217 patients who were hospitalized for CVD treatment were enrolled. We assessed frailty status by using the Fried criteria and respiratory muscle strength by measuring the maximal inspiratory pressure (PImax) at hospital discharge, with RMW defined as PImax <70% of the predicted value. The endpoint was a composite of all-cause death and/or readmission for heart failure. We examined the prevalence of RMW and frailty and their correlation. The relationships of RMW with the endpoint for each presence or absence of frailty were also investigated. Respiratory muscle weakness and frailty were observed in 456 (37.5%) and 295 (24.2%) patients, respectively, and 149 (12.2%) patients had both statuses. Frailty was detected as a significant indicator of RMW [odds ratio: 1.84, 95% confidence interval (CI): 1.39-2.44]. Composite events occurred in 282 patients (23.2%). Respiratory muscle weakness was independently associated with an increased incidence of events in patients with both non-frailty [hazard ratio (HR): 1.40, 95% CI: 1.04-1.88] and frailty (HR: 1.68, 95% CI: 1.07-2.63).

CONCLUSIONS

This is the first to demonstrate a correlation between RMW and frailty in patients with CVD, with 12.2% of patients showing overlap. RMW was significantly associated with an increased risk of poor outcomes in patients with CVD and frailty.

Excess ventilation and exertional dyspnoea in heart failure and pulmonary hypertension

Increased ventilation relative to metabolic demands, indicating alveolar hyperventilation and/or increased physiological dead space (excess ventilation), is a key cause of exertional dyspnoea. Excess ventilation has assumed a prominent role in the functional assessment of patients with heart failure (HF) with reduced (HFrEF) or preserved (HFpEF) ejection fraction, pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). We herein provide the key pieces of information to the caring physician to 1) gain unique insights into the seeds of patients' shortness of breath and 2) develop a rationale for therapeutically lessening excess ventilation to mitigate this distressing symptom. Reduced bulk oxygen transfer induced by cardiac output limitation and/or right ventricle-pulmonary arterial uncoupling increase neurochemical afferent stimulation and (largely chemo-) receptor sensitivity, leading to alveolar hyperventilation in HFrEF, PAH and small-vessel, distal CTEPH. As such, interventions geared to improve central haemodynamics and/or reduce chemosensitivity have been particularly effective in lessening their excess ventilation. In contrast, 1) high filling pressures in HFpEF and 2) impaired lung perfusion leading to ventilation/perfusion mismatch in proximal CTEPH conspire to increase physiological dead space. Accordingly, 1) decreasing pulmonary capillary pressures and 2) mechanically unclogging larger pulmonary vessels (pulmonary endarterectomy and balloon pulmonary angioplasty) have been associated with larger decrements in excess ventilation. Exercise training has a strong beneficial effect across diseases. Addressing some major unanswered questions on the link of excess ventilation with exertional dyspnoea under the modulating influence of pharmacological and nonpharmacological interventions might prove instrumental to alleviate the devastating consequences of these prevalent diseases.

Ultrasound-assessed diaphragm dysfunction predicts clinical outcomes in hemodialysis patients

Skeletal muscle atrophy is prevalent and remarkably increases the risk of cardiovascular (CV) events and mortality in hemodialysis (HD) patients. However, whether diaphragm dysfunction predicts clinical outcomes in HD patients is unknown. This was a prospective cohort study of 103 HD patients. After assessment of diaphragm function by ultrasonography and collection of other baseline data, a 36-month follow-up was then initiated. Participants were divided into diaphragm dysfunction (DD+) group and normal diaphragm function (DD−) group, according to cutoff value of thickening ratio (i.e. the change ratio of diaphragm thickness) at force respiration. The primary endpoint was the first nonfatal CV event or all-cause mortality. A secondary endpoint was less serious CV events (LSCEs, a composite of heart failure readmission, cardiac arrhythmia or myocardial ischemia needed pharmacological intervention in hospital). 98 patients were eligible to analysis and 57 (58.16%) were men. 28 of 44 patients(63.64%) in DD+ group and 23 of 54 patients (42.59%) in DD− group had at least one nonfatal CV event or death (p = 0.038). Compared to DD− group, DD+ group had significantly higher incidence of LSCEs (21 vs.14, p = 0.025) and shorter survival time (22.02 ± 12.98 months vs. 26.74 ± 12.59 months, p = 0.046). Kaplan–Meier analysis revealed significantly higher risks of primary endpoint (p = 0.039), and LSCEs (p = 0.040) in DD+ group. Multivariate hazard analysis showed that DD+ group had significantly higher risk of primary endpoint [hazard ratio (HR) 1.59; 95% confident interval (CI) 1.54–1.63], and LSCEs (HR 1.47; 95%CI 1.40–1.55). Ultrasound-assessed diaphragm dysfunction predicts clinical outcomes in HD patients.

Trial registration: This study was registered with Chinese Clinical Trials Registry (www.chictr.org.cn) as ChiCTR1800016500 on Jun 05, 2018.

Dyspnea in patients with atrial fibrillation: Mechanisms, assessment and an interdisciplinary and integrated care approach

Atrial fibrillation (AF) is the most common sustained heart rhythm disorder and is often associated with symptoms that can significantly impact quality of life and daily functioning. Palpitations are the cardinal symptom of AF and many AF therapies are targeted towards relieving this symptom. However, up to two-third of patients also complain of dyspnea as a predominant self-reported symptom. In clinical practice it is often challenging to ascertain whether dyspnea represents an AF-related symptom or a symptom of concomitant cardiovascular and non-cardiovascular comorbidities, since common AF comorbidities such as heart failure and chronic obstructive pulmonary disease share similar symptoms. In addition, therapeutic approaches specifically targeting dyspnea have not been well validated. Thus, assessing and treating dyspnea can be difficult.

This review describes the latest knowledge on the burden and pathophysiology of dyspnea in AF patients. We discuss the role of heart rhythm control interventions as well as the management of AF risk factors and comorbidities with the goal to achieve maximal relief of dyspnea. Given the different and often complex mechanistic pathways leading to dyspnea, dyspneic AF patients will likely profit from an integrated multidisciplinary approach to tackle all factors and mechanisms involved. Therefore, we propose an interdisciplinary and integrated care pathway for the work-up of dyspnea in AF patients.

Pathophysiology and Clinical evaluation of the patient with unexplained persistent dyspnea

INTRODUCTION

Dyspnea is a complex symptom, which largely results from an imbalance between an afferent sensory stimulus and the corresponding efferent respiratory neuromuscular response. In addition, it is heavily influenced by the patient's prior experiences and sociocultural factors.

AREAS COVERED

The diagnostic approach to these patients requires a graded, systematic, and often multidisciplinary approach to determine what is the underlying pathophysiologic process. Utilization of objective data obtained through lab testing, imaging, and advanced testing, such as cardiopulmonary exercise testing, is often required to help identify underlying pathology contributing to a patient's symptoms. This article will review dyspnea's underlying pathophysiological mechanisms and standardized approaches to diagnoses. In the expert opinion section, we will discuss our own clinical approach to evaluating patients with persistent dyspnea.

EXPERT OPINION

Unexplained dyspnea is a challenging diagnosis that occurs in patients with and without underlying cardiopulmonary diseases. It requires a systematic approach, which initially uses clinical evaluation in addition to standard imaging and clinical biomarkers. When diagnoses are not made during the initial evaluation, subsequent tests can include cardiopulmonary exercise test and methacholine challenge. To be certain of the correct diagnosis, It is imperative that the clinician determines dyspnea's response to a particular therapeutic intervention.